Quartz crystal resonators and filters used in electronic circuits are positioned within a mounting structure which provides both an electrical connection to and mechanical support for the crystal plate. The mounting used is a factor in determining the mechanical reliability of the crystal unit when subjected to shock or vibration. Prior art mounting structures generally are of the type shown and described in U.S. Pat. No. 3,336,487, issued to L. G. Martyn, et al, and assigned to the same assignee as this application. In the Martyn patent, a crystal plate is supported on a mounting base through which conducting pins extend for making electrical connections to the electrodes. Resilient wires secure the conducting pins to the crystal. These resilient wires extend upwards on both sides of the crystal plate from the base. A cover is secured to the mounting base and forms an enclosure for the crystal plate. It is necessary to have flexible supports to prevent any appreciable stress being applied to the crystal plate due to the differential expansion of the mounting base and crystal plate with changing temperature. Should the crystal unit be dropped, the resilient wires supporting the crystal plate will deflect upon impact and may cause fracture of the plate due to its bending or striking the cover.
When a crystal plate is mounted in the structure such as described above, it is then tested to determine whether it is operating at the correct frequency. If it is not operating at the correct frequency, the thickness of the electrodes is adjusted until the crystal operates at the correct frequency. In order to perform this adjustment procedure, both sides of the crystal must be exposed, after it is mounted in the desired mounting structure. The structure described above allows such testing and operating frequency corrections. However, in order to provide this capability, the cover which is secured to the mounting base to form the enclosure for the crystal plate, is made quite large making the entire crystal unit quite bulky.
Further, in all prior art assembly techniques, crystal unit packages must be assembled and tested one at a time. This greatly increases the labor and the cost of the final package.